1. Field of the Invention
The present invention relates to a master digital data creation device and a digital data reproduction device, and more particularly to a master digital data creation device and a digital data reproduction device that prevent the illegal reproduction or copy of distributed digital data such as audio data and video data.
2. Description of the Related Art
Recently, more and more recording and reproduction devices and their media have become available for processing digital data. These devices and media give audio and video users many benefits such as high-speed, non-degraded recording and reliable reproduction. On the other hand, a problem has arisen that many non-degraded copies are produced quickly and sold with no permission from copyright holders. The prevention of illegal copy has become critical.
To prevent illegal copy, the SCMS (Serial Copy Management System) is used for conventional digital recording and reproduction devices such as a digital audio tape recorder (DAT) and a minidisk (MD). In the SCMS, copy permission status information is recorded in a particular area on a medium. That is, when the copy permission status information recorded on a copy source medium is “00”, the same copy permission status information “00” is recorded also on a copy destination medium to permit the user to create another copy from the copy destination medium (so called copy free).
When the copy permission status information recorded on a copy source medium is “10”, the copy permission status information is changed to “11” on a copy destination medium to inhibit the user from creating another copy from the copy destination medium (that is, copy is permitted only once). This system is established on the assumption that, upon detection of the copy permission status information of “11” on a medium, an SCMS-conforming device stops the copy operation.
Other conventional copy prevention methods include digital data encryption. This is accomplished by scrambling copy-protecting digital data with the use of a predetermined control word and, at the same time, by encrypting the control word with particular key data.
FIG. 1 shows the overview of an exemplary conventional copy protection method. In a mastering device 1 shown in the figure, a scrambler 2 scrambles digital data P, such as audio service (contents) data, using a control word P and outputs scrambled digital data C to a recording medium 4. At the same time, an encryption unit 3 encrypts the control word P using key data K and outputs a control word C to the recording medium 4.
In a reproduction device 5, a decryption unit 6 receives the control word C reproduced from the recording medium 4 and decrypts it to the control word P using the key data K. At the same time, in the reproduction device 5, a de-scrambler 7 receives the digital data C reproduced from the recording medium 4 and produces the digital data P using the control word P already produced by the decryption unit 6. Algorithms suitable for this processing include DES(Data Encryption Standard), RSA(named after Ron Rivest, Adi Shamir, and Len Adleman). When data is copied from this recording medium 4 to another recording medium, only the digital data C is copied, without the control word C. When reproducing data from the copy destination medium, de-scrambling processing cannot be performed correctly and therefore the user cannot receive services (Digital data P cannot be reproduced correctly). In this way, the copy operation is virtually prevented.
However, when the copy permission status information is rewritten in the SCMS, that is, when the information is altered, the following problem arises. For example, once the copy permission status information on the copy source medium, even if “10”, is rewritten to “00” either when it is copied to a copy destination medium or by a processor on a transmission line, data may be illegally copied thereafter.
In addition, the conventional method for scrambling digital data in which all copies are prevented, the user is not permitted to create even a personal backup copy against an accidental destruction of a recording medium. This is unreasonable because the merit of using digital data is impaired. What is important is that copy operation should not be limited but that the copyright holder of digital contents should be paid for the service the user receives. This means that a copy management method other than that described above is required.
In the prior art, a method is disclosed which solves this problem by charging the user for the reproduction of digital contents reproduction, calculating the total of the usage amount, and distributing the charge among copyright holders (Japanese Patent Laid-Open Publication No. Hei 10-269289).
However, the conventional method and device, which return the digital contents usage status to a charge manager, require communication between the reproduction device and the charge manager and therefore makes processing complex.